The invention pertains to the art of printing and, more particularly, to an electrode arrangement and contragraphy instrument.
An example of contragraphy process is disclosed in DE-OS 34 11 948. In the contragraphy process, an electrical field is developed through the paper, between the developer surface, which transports a thin layer of electrically charged toner particles, and suitable print electrodes. The respective print electrode develops the required drawing field. If the electrical field force is strong enough at the location of the developer surface in order to overcome the adhesive power of the toner, the toner is torn off at that location and accelerated in the direction of the paper. The shape of the reproduction of the toner on paper is basically determined by the spatial shape and force of the electrical field between print electrode and developer surface. A description is given in DE-OS 34 11 948 of the utilization of one or several, vis-a-vis the developer surface, vertically oriented needles of electrically conducting material (metal). In order to ensure appropriate through-put during the contragraphy process, several print electrodes must operate simultaneously. For example, for printing of DIN A 4 format pages with a resolution of 200 dpi on a page-at-a-time printer, 1654 of such print electrodes are needed.
With this type of matrix of print electrodes, it is, however, difficult to guarantee accurate position of electrodes to each other. Mass production of such an array of electrodes combined with difficulty in automated contacting of individual electrodes is the reason why contragraphy printing in this form has not as yet been able to establish itself on the market.